Method of preventing rotational vibrations in a thread storage and feed device and a thread storage and feed device

ABSTRACT

In the case of a method of holding in position a rotatably supported thread storage surface in a thread storage and feed device, in which a group of components defining the storage surface is rotatably supported on a shaft adapted to be rotated in a housing and in which a winding-on member circulates together with the shaft, whereas magnets prevent the group of components from rotating together with the shaft, a rotational vibration damping connection is temporarily established between the housing and the group of components while the shaft is rotating In a thread storage and feed device (F), which is provided with an advance member (6) adapted to be driven such that it carries out a wobbling movement, there are arranged an externally supported rotational vibration damping member (X) and an abutment (Y) which is provided on the advance member (6). When the device (F) is equipped with a stop device including a movable stop element (23), the stop element (23) constitutes the rotational vibration damping member (X, 50).

DESCRIPTION

The present invention is directed to a thread storage and feed device.

In the case of a method of the type mentioned at the beginning, which isknown from U.S. Pat. No. 4,226,379, the magnets which are fixedlysecured to the housing are located radially outside of the group ofcomponents, and the magnets arranged in said group of components arelocated below the storage surface. The magnetic holding forces act atthe largest possible distance from the shaft The characteristic curve ofthe holding force counteracting a rotation of the group of componentsascends first flatly and, afterwards, steeply. In the case of modernthread storage and feed devices, high rotational speeds of the shaftoccur due to extremely high thread velocities Due to unavoidableunbalanced masses, the thread counterforce which is variable in thedirection of rotation, the cantilevered mode of support of the group ofcomponents on the shaft, accelerations and decelerations occurring inoperation, and other interfering influences, rotary force pulses actingon the group of components may occur, said group of components beingthen prompted to carry out oscillating movements into both directions ofrotation from the holding position defined by the magnets. In view ofthe holding force characteristic, the group of components will beginbuilding-up rotational vibrations around the desired position, whichwill reach a resonance state having a large amplitude, e.g. severalmillimetres. The rotational vibrations cause high strain on the holdingmeans of the magnets, and they make it more difficult to sense thethread supply precisely as well as to maintain a thread take-off tensionwhich is as uniform as possible In cases in which the thread storage andfeed device is equipped with an integrated weft thread metering device,the rotational vibrations will interfere with the weft thread meteringoperation

It is true that German-pat. 28 43 548 discloses a method of holding inposition the group of components in a thread storage and feed device; inthe case of said method, the group of components is supported on thehousing continuously and in a purely mechanical manner Although thismethod avoids the disadvantage of a magnetic holding force which is weakaround the desired position, it results in a complicated and veryspecial structural design of the device

The present invention is based on the task of providing a method of thetype mentioned at the beginning, which, when the group of components isheld in position by means of magnetic holding forces, will avoidinterfering rotational vibrations, as well as a thread storage and feeddevice, which includes a group of components held in positionmagnetically and which permits, even at high speeds, an operationlargely free from rotational vibrations.

The posed task is solved by the features disclosed by the presentinvention.

The temporarily established rotational vibration damping connectionbetween the housing and the group of components prevents the building upof rotational vibrations of the group of components against the holdingforce of the magnets which is weak around the desired position. In viewof the fact that the rotational vibrations need a certain amount of timefor reaching a resonance state and a troublesome amplitude, the build-uptendency is interfered with from the very beginning by the temporaryrotational vibration damping connection so that the generation ofdetrimental rotational vibrations will be prevented completely Theforces applied to the group of components during the temporaryrotational vibration damping connection can be comparatively small,since the comparatively free oscillation system of the group ofcomponents is influenced by said forces in an extremely efficient mannerand in such a way that said group of components can actually no longerbe prompted to carry out any noticeable oscillations at all.

In view of the fact that, on the one hand, the thread, which movescontinuously around the group of components on its way from thewinding-on member to the consumer, makes direct access extremelydifficult, and in view of the fact that, on the other hand, thebuilding-up of troublesome rotational vibrations needs a specific amountof time, it will suffice to establish the rotational vibration dampingconnection only over a fraction of one full rotation of the shaft and atleast once.

In view of the time required for building up troublesome rotationalvibrations, it will suffice to establish the rotational vibrationdamping connection at intervals which are longer than those determinedby the rotational speed of the shaft. These intervals can be regular orirregular.

The rotational vibration damping connection will be time controlled in areliable manner, when it is established pneumatically, mechanically ormagnetically.

When the thread is withdrawn intermittently from a thread supply formedon the storage surface, it will be expedient to establish the rotationalvibration damping connection in respective pauses in the threadwithdrawal operation. This can then be done on the withdrawal side ofthe storage surface and precisely at a location at which no thread ispresent.

In the case of a thread storage and feed device comprising an advancemember in the group of components, it will be expedient to provide arotational vibration damping member, which is supported in a stationarymanner relative to the group of components and which is in alignmentwith an abutment on said advance member, as well as a motion drive meanswith the aid of which a positive and/or non-positive engagement can beestablished temporarily so as to already disturb the rotationalvibrations when they arise and so as to destroy them to a large extent.The advance member is prevented from rotating together with the shaftanyhow, and it is driven such that it will carry out a wobbling movementand advance the thread on the storage surface. In this connection, itwill be expedient to use the wobbling movement for the temporarypositive and/or non-positive engagement. The shaft will then so to speakconstitute the motion drive means for the temporary cooperation betweenthe rotational vibration damping member and the advance member. If theadvance member is of a different nature, e.g. a rod-type cage, which issupported on the shaft eccentrically and at an oblique angle and whichis used not only for imparting to the thread the advance movement butalso for establishing intervals between the thread windings, thewobbling movement may perhaps not suffice to produce the temporarypositive and/or non-positive engagement. If this is the case, it will beexpedient to forcibly engage and disengage the rotational vibrationdamping member. In the first-mentioned case, engagement will beestablished at least once virtually during each rotation of the shaft.In the last-mentioned case, the intervals between the individualengagements are largely independent of the rotational speed of theshaft. In view of the fact that the interfering rotational vibrationshave been eliminated, the strain on the holding means of the magnetswill be reduced, perfect sensing of the thread will be possible, andundesirable variations in the tension of the thread withdrawn will beeliminated.

When the rotational vibration damping member enters the wobblingmovement area of the advance member from outside, a temporary engagementwill be established in the case of each rotation of the shaft, saidtemporary engagement preventing the generation of rotational vibrations.Notwithstanding this, the storage surface and the other components ofthe group of components remain easily accessible from outside, in viewof the fact that the rotational vibration damping member requires littlespace and can easily be incorporated into the concept of the device.

Alternatively, it is also possible to arrange the rotational vibrationdamping member such that it is movable so as to forcibly establish theengagement.

A structurally simple possibility is that in the case of which therotational vibration damping member is secured in position in a holdingmeans of the housing because the housing is held in a stationary mannerand constitutes a comparatively big mass by means of which the forcesoccurring as a result of the damping of any kind of rotationalvibrations can easily be taken up. However, the rotational vibrationdamping member may just as well be held on a support, which is separatedfrom the housing and which is arranged in a stationary manner just likesaid housing.

In the case of a particularly simple embodiment, which is space-savingand reliable in function, the rotational vibration damping member is aU-shaped bow, which consists of a resilient material and the crossbow ofwhich cooperates with the abutment The inherent resilience of the bowwill avoid any interfereing influence on the operation of the advancemember. Notwithstanding this, the engagement between these two partswill suffice to suppress the rotational vibrations.

A continuously uniform damping effect will be achieved by a frictionallyactive area n the rotational vibration damping member and/or on theabutment. The force transmitted between these two parts in the engagedcondition can be small because the frictional engagement will supportthe damping effect.

The often limited space conditions are taken into account by thesolution in the case of which the bow extends approximately radially tothe advance member on the axial side of the winding-on member facing thestorage surface and is bent towards said advance member. In this area,and in view of the fact that the dimensions of the rotational vibrationdamping member are limited in the circumferential direction, there willneither be any major impairment of access to the group of components norwill the path of motion of the thread be interfered with.

The engagement force can be very small, when a positive engagement isestablished between the rotational vibration damping member and theabutment, said positive engagement interrupting abruptly the movement ofthe group of components away from the desired position.

Alternatively, it will also be expedient to establish the engagement viamagnets which contact each other in the condition of engagement.

In order to avoid collisions with the thread or with the winding-onmember, it will be important to control the motion drive means of therotational vibration damping member in a specific manner.

In view of the fact that, for suppressing troublesome rotationalvibrations, it will suffice to establish the engagement at largerregular or irregular intervals than the rotational speed of the shaft,the motion drive mans can include a pulse control.

In view of the fact that, for suppressing the troublesome rotationalvibrations, it will be important to apply an interference force inaddition to the magnetic holding force which is weak around the desiredposition, the rotational vibration damping member can also be acompressed-air nozzle directing a flow onto the abutment constructed asa guide element.

In a thread storage and feed device, in the case of which the abutmenton the group of components does not carry out any movement of its ownwhich would suffice to establish a temporary engagement, the rotationalvibration damping member is moved approximately radially to the shaftbetween an in-operative position and a position of engagement with theaid of a motion drive means connected to a control Measures have beentaken to prevent the rotational vibration damping member from collidingwith the moving thread or the winding-on member. For the suppression oftroublesome rotational vibrations, it is of secondary importance inwhich area or the group of components the inteference force is applied.It will, however, be expedient to apply said interference force at thelargest possible radial distance from the shaft. The period ofengagegment can be extremely short In practice, it will suffice to touchthe group of components only briefly, e.g. for a few milliseconds.

In this connection, it will be advantageous to use a magnet or amagnetic coil for which the rotational vibration damping member definesa pushrod-shaped armature. It is thus posible to achieve short andprecisely controlled periods of engagement The control can be effectedby means of the signals which are used in the device for the operationalcontrol thereof anyhow.

In order to reliably apply the interference force in the case of shortperiods of engagement, it will be expedient to establish between thehead of the rotational vibration damping member and a recess in thestorage surface a positive and/or non-positive engagement. The group ofcomponents will thus immediately be centered in the desired position.

This effect will be produced in a particularly precise manner, when therecess is adapted to the shape of the head.

Alternatively, it is also imaginable to provide an elastic, frictionallyactive pad in the recess or on the head. This will protect therotational vibration damping member and the group of components. Theinterfernce force pulse is particularly suitable for suppressing thegeneration of the troublesome rotational vibrations. Moreover,undesirable noise and wear is avoided.

In a thread storage and feed device in the case of which the storagesurface has associated therewith a thread stopping device including astop element, it will be expedient to displace the rotational vibrationdamping member axially or/and in the circumferential direction relativeto the stop element so as to avoid mutual interference. It will beadvantageous to establish engagement of the rotational vibration dampingmember at a moment at which the thread is secured in position by thestop element. The period of engagement used may be the same period whichis predetermined for holding the thread in position. The engagement neednot necessarily be established in the case of each actuation of the stopdevice. Also longer intervals between the individual engagements willsuppress the generation of interfering rotational vibrations.

The rotational vibration damping member plus its motion drive means canalso be integrated in the stop device; this will save space and permitfree access to the group of components.

Finally, according to a double function of the stop element, therotational vibration damping member can be defined by the stop elementof the stop device itself. For holding the thread in position, the stopelement is required in the circumferential direction of the storagesurface as an obstacle. For suppressing interfering rotationalvibrations, the engagement between the stop element and the storagesurface is used at a point locally separated therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the subject matter of the invention explained on thebasis of the drawing, in which:

FIG. 1 shows a longitudinal section through a thread storage and feeddevice,

FIG. 2 shows one half of a front view of FIG. 1,

FIG. 3 shows an enlarged fragmentary longitudinal section taken fromFIG. 1 and 2 in a different operating position,

FIG. 4 shows a perspective view of a detail taken from FIG. 3,

FIGS. 5a-5i show sectional views of various embodiments of therotational damping member and the abutment associate therewith,

FIG. 6 shows a schematic representation of an additional detailvariation,

FIG. 7 shows a longitudinal sectional view of an additional embodimentof a thread storage and feed device, and

FIG. 8 shows a front view of FIG. 7, FIG. 7 and 8 showing two structuralvariations side by side.

DETAILED DESCRIPTION

A thread storage and feed device F according to FIG. 1 to 3 contains ina housing G, which is supported in a stationary manner, a drive motor Mfor a shaft 1 carrying an obliquely projecting winding tube 2. Thehousing has arranged therein a control means C for the drive motor M,said control means C being in signal-receiving connection with sensormeans, which are not shown in detail. The winding tube 2 is integratedin an annular body R containing a winding-on member W. The housing hasprovided thereon a support A for a rotational vibration damping memberX, which is adapted to be temporarily brought into engagement with anabutment Y so as to establish a rotational vibration damping connectionD (FIG. 3).

A group of components K is supported, in bearings 3, on the free end ofthe shaft 1 projecting beyond the annular body R, said group ofcomponents K comprising, in addition to constituent parts which are notspecified in detail, a storage member 4, which consists of individualsegments and which is provided with axially extending arms 4b. Said arms4b define a polygonal storage surface S. Furthermore, an advance member6 is rotatably supported, in bearings 5, on the free end of the shaft 1,said advance member 6 projecting outwards beyond the storage surface Sup to a point in the vicinity of the annular body R. The axis ofrotation 6a of the advance member 6 extends at an oblique angle relativeto the axis of rotation Ia of the shaft I in such a way that the advancemember 6 is tilted towards the winding-on member W. The housing G hasmagnets 10 arranged therein, said magnets 10 being in alignment withmagnets 11 in the group of components K. Between the magnets 10, 11, agap is provided, which permits the winding tube 2 to be passed throughand across which magnetic holding forces are effective, which preventthe group of components K and the advance member 6 from rotatingtogether with the shaft 1. When the shaft 1 rotates, the advance member6, which is prevented from rotating together with the shaft, is promptedto carry out a wobbling movement (wobbling area 7).

A thread 8 supplied through the hollow shaft 1 extends through thewinding tube 2 and the winding-on member W by means of which said threadis placed onto the storage surface S in the form of a thread supply 9consisting of individual windings. A dot-and-dash line indicates how thethread is withdrawn overhead from the storage surface S. When carryingout its wobbling movement, the advance member 6 continuously advancesthe thread supply 9 from the winding-on member W in the axial direction.

The rotational vibration damping member is a U-shaped bow 12 (FIG. 2),which is formed of spring-steel wire and which is clamped in position ina reception means 14 of the housing by means of a locking or holdingelement 31 and a locking screw 15. The U legs of the bow 12, which areprovided with reference numerals 16 and 17, are bent and extend acrossthe circulatory path of the winding-on member W to the advance member 6.A crossbow 18, which interconnects the legs 16, 17, extendsapproximately tangentially to the shaft 1 Said crossbow 18 is providedwith a frictionally active area, e g. coating 19 having high frictionalproperties. The bow 12 is bent towards the advance member 6 in the areaof the crossbow 18.

The device F according to FIG. 1 is constructed as a weft threadmetering device releasing from the thread supply 9 individual sectionsof precisely dimensioned length for withdrawal. For this purpose, thehousing has provided thereon a stop device 21, which has attachedthereto a magnetic coil or a magnet as a motion drive means 22 for apushrod-shaped stop element 23. The stop element 23 is adapted to bemoved into a recess 24, which is provided in said storage surface S, soas to stop the thread 8 which circulates while being withdrawn. When thestop element 23 is drawn back, the thread will pass unhindered.

In FIG. 2, it can be seen that the longitudinal rods 4b of the storagemember 4 engage radial slots 20 of the advance member 6. The annular rimof the advance member 6, which is provided with reference numeral 6a,(FIG. 4) serves at one point of the circumference as the abutment Y forthe rotational vibration damping member X. If desired, africtionally-active coating is provided at this location, or a recess,which is adapted to be brought into positive engagement with the bow 12,when the rim 6a comes into contact with said bow 12 in the wobbling area7 of the advance member 6 so as to establish a temporary rotationalvibration damping connection.

The diameter of the storage surface S is variable. For this purpose, thesegments of the storage member 4 are adapted to be radially adjusted

In FIG. 3, the winding-on member W has been rotated by approx. 180°relative to its position in FIG. 1. The advance member 6 has movedaxially relative to the bow 12 until the rotational vibration dampingconnection D has been established by engagement between the crossbow 18and the surface 6a. The crossbow 18 has a length which is limited in thecircumferential direction of the advance member 6 to a small number ofangular degrees in such a way that the engagement will be maintainedthroughout approx. 1/4 of one full rotation of the shaft 1 before theadvance member 6 separates from said crossbow 18 and opens a gap(FIG. 1) in which the thread 8 will pass the bow 12 without beingcaught. In the condition of engagement, rotational vibrations of thegroup of components K which normally would be in the process ofdeveloping are suppressed so that the group of components will holdstill in the desired position determined by the magnets 10, 11.

According to FIG. 3, elastic filling members 26, 27 are arranged in theinterior of the group of components. Thanks to the elasticity of saidfilling members 26, 27, the wobbling movement of the advance member 6 isnot impaired.

FIG. 5a to 5i show various embodiments of the rotational vibrationdamping member X and of the abutment Y associated therewith.

In FIG. 5a, the rotational vibration damping member X is a pin 28, thehead of said pin 28 having attached thereto a friction coating 29, whichis pressed onto a flat surface 30 of the abutment Y.

In FIG. 5b, the rotational vibration damping member X is a pushrod 31whose head 32 enters a preferably conically enlarged recess 33 of theabutment Y.

In FIG. 5c, the rotational vibration damping member X is a pushrod 34having a rounded head 35, which is pressed into an elastic coating 36 ofthe abutment Y.

In FIG. 5d, the rounded head 35 of the rotational vibration dampingmember X is inserted into a recess or in a hole 37 of the abutment Y.The walls of the hole can be rounded or conically enlarged.

In FIG. 5e, the rotational vibration damping member X has the shape of amushroom 39 with a recess 40, which is formed at the bottom thereof andwhich is placed onto a projection 38 of the abutment Y.

In FIG. 5f, the rotational vibration damping member X is a pin 41 havingan oblique head 42. The abutment Y has the form of a saw-tooth recess 43with a stop means 44 provided at one side thereof For suppressing therotational vibrations, it will suffice to guarantee a reliable positiveengagement in only one direction of rotation.

In FIG. 5g, the rotational vibration damping member X is a pushrod 45carrying a magnet 46 at the head thereof. The abutment Y is either madeof magnetic material or equipped with a magnet 47 by means of which anon-positive engagement is established when the magnet 46 is in contacttherewith. The abutment Y can be contained in the advance member 6.

According to FIG. 5h, the rotational vibration damping member X is acompressed-air nozzle 48, which is connected to a pressure source Q andwhich is in alignment with the abutment Y having the form of a guideelement 49. The jet discharged from said nozzle 48 produces on the guidesurface 49 an interference force which will prevent the development ofrotational vibrations. The slots 20 in the advance member 6 serve asflow passages at both sides of the guide element 49.

According to FIG. 5i, the rotational vibration damping member X is apushrod 50 whose head 51 is adapted to be inserted into a recess 52 ofthe abutment Y. An elastic friction coating 53 is provided at the bottomof the recess 52. The abutment Y can be arranged either in the advancemember 6 or--as indicated in this FIG. 5i--in one of the longitudinalrods 4b of the storage member 4. The rotational vibration damping memberX requires a motion drive means imparting thereto the movementsindicated in the direction of the double arrow.

In FIG. 6, a motion drive means for a rotational vibration dampingmember X, which is constructed as a double lever 54, is schematicallyoutlined. The double lever 54 is adapted to be pivoted in the support Aabout an axis 55 and one end thereof is acted upon by a motion drivemeans 56 including a pulse control. A readjusting spring 57 counteractsthe motion drive means 56. The abutment Y can be arranged either on theadvance member 6 or on a longitudinal rod 4b of the storage member 4.

In the case of an additional embodiment of a thread storage and feeddevice F according to FIG. 7 and 8 wherein said stop element 23 is notpermitted to contact the storage surface S, the rotational vibrationdamping connection D is established between a support A, 58, which isstationary relative to the group of components K, and the storagesurface S. The rotational vibration damping member X has the structuraldesign shown in FIG. 5i, i.e. the head of the pushrod 50 is radiallybrought into contact with the storage surface S so as to establish theengagement. In the support 58, which may be, but need not be part of thehousing G, a holding means 59 for a motion drive means 60 is held. Itwill be expedient to connect the motion drive means 60 to a control,which will actuate the rotational vibration damping member X only if thethread 8 is just standing still in a pause in the withdrawal. The restof the structural design of the device F according to FIG. 7 correspondsto the structural design of FIG. 1 to 3. When the device F is equippedwith a stop device 21, the rotational vibration damping member X will bebrought into engagement whenever the stop element 23 stops the threaddelivered. According to FIG. 7 and 8, the rotational vibration dampingmember X is displaced relative to the stop device 21 in thecircumferential direction It is also imaginable to displace therotational vibration damping member relative to the stop device 21 inthe axial direction. In FIG. 7 the displacement amounts to 180° in thecircumferential direction, in FIG. 8 it amounts only to 90°.

In the case of this embodiment, the rotational vibration damping memberX, is arranged separately from the stop device 21 in a support A, 58 ofits own. This principle may also be used for a thread storage and feeddevice which does not include any stop device, provided that the motiondrive means 60 is controlled in response to the thread withdrawalmotion.

However, it is possible to structurally integrate the rotationalvibration damping member X plus its motion drive means 60 into the stopdevice 21 by permitting the stop element 23 to contact the storagesurface thus carrying out the dual functions of stopping the thread 8,and suppressing rotational vibrations. It will be particularlyexpedient, when the stop element 23 simultaneously defines therotational vibration damping member X by positively cooperating with therecess 24 or by being pressed onto an elastic coating 53 within saidrecess 24 as shown in FIG. 5i, so that the temporary rotationalvibration damping connection D will be established whenever the threadhas to be stopped In this case, no additional rotational vibrationdamping member X will be required.

We claim:
 1. In a thread storage and feed device including a housingrotatably supporting a driven shaft having a thread winding-on membercoupled thereto, a component group rotatably supported on said shaft andincluding at least one thread storage member defining a thread storagesurface, a thread advance member extending obliquely relative to saidshaft and driven such that it carries out a wobbling movement relativeto the thread storage surface, said thread advance member projectingradially beyond said thread storage surface, and at least one magnetarranged within said component group and cooperating with at least onemagnet fixedly secured to said housing to prevent said component groupfrom rotating with said shaft, the improvement comprising: a supportwhich is stationary relative to said component group; at least onerotational vibrational damping member coupled to said support, saiddamping member being of limited extent in a circumferential direction ofsaid storage surface; an abutment disposed on said thread advance memberwhich is in alignment with said damping member; and a motion drive meansfor temporarily bringing said abutment into vibration-damping engagementwith said first damping member during only a portion of one completerotation of said shaft.
 2. The device as claimed in claim 1, furtherincluding a holding means for releasably and adjustably coupling saiddamping member to said support.
 3. The device as claimed in claim 2,wherein said damping member is a U-shaped bow having first and secondspaced-apart legs each being fixedly secured to said support by saidholding means, and a crossbow traversely coupled to said legs at freeends thereof, said crossbow positioned approximately tangentially withrespect to an axis of rotation of said shaft and which is in alignmentwith said abutment, said abutment contacting said crossbow during saidportion of one complete rotation of said shaft.
 4. The device as claimedin claim 3, wherein said U-shaped bow is made of a resilient materialsuch as spring-steel wire, said resilient material permitting saiddamping member to be temporarily displaced when said abutment contactssaid crossbow.
 5. The device as claimed in claim 3, wherein at least oneof said crossbow and said abutment include a coating having highfrictional properties.
 6. The device as claimed in claim 3, wherein saidU-shaped bow radially extends from said support to said advance memberalong a side of said winding-on member facing said storage surface, saidcrossbow being angled toward said advance member.
 7. The device asclaimed in claim 1, wherein said damping member and said abutmentinclude opposing surfaces for causing positive engagement therebetweenin the direction of rotation of said shaft.
 8. The device as claimed inclaim 7, wherein at least one of said opposing surfaces includes amagnet.
 9. The thread storage and feed device as claimed in claim 1,wherein said damping member is a compressed-air nozzle, and saidabutment is a guide element for an air flow discharged from said nozzle.10. A method of temporarily disturbing the generation, development orcontinuation of rotational vibrations that develop within a threadstorage and feed device, said thread storage and feed device including ahousing rotatably supporting a driven shaft having a thread winding-onmember coupled thereto, a component group rotatably supported on saidshaft and including at least one thread storage member defining a threadstorage surface, a thread advance member extending obliquely relative tosaid shaft and driven such that it carries out a wobbling movementrelative to the thread storage surface, said thread advance memberprojecting radially beyond said thread storage surface, and at least onemagnet arranged within said component group, and cooperating with atleast one magnet fixedly secured to said housing to prevent saidcomponent group from rotating with said shaft, said method comprisingthe steps of:rotating said shaft; causing said thread advance member tocarry out said wobbling movement in response to said shaft rotation; andcausing an abutment disposed on a circumference of said thread advancemember to temporarily engage a rotational vibrational damping membermounted on said frame during only a portion of one complete rotation ofsaid shaft.